Understand the idea.
Read the model
In this part–whole model, the top circle shows everything. The lower circles show the two parts that make it. The connecting lines tell you the parts belong together; they do not mean that there are extra objects to count.
A blank changes the question
Look for the empty place before choosing a calculation. To find a whole, join the two parts. To find a missing part, count on from the known part to the whole, or take the known part away from the whole.
See the method in action.
Read the complete model
The whole is fourteen. One part is nine. What is the other part?
Worked solution
- 1
Name the whole and the known part.
Nine is already included in the whole fourteen.
- 2
Count on from nine to fourteen.
There are five steps between the known part and the whole.
- 3
Check the other part.
The two parts join to make fourteen, so the missing part is five.
5
Find a whole
The two parts are eight and seven. Find the whole.
Worked solution
- 1
Join the two parts.
The missing whole contains all eight and all seven objects.
- 2
Use two from the seven to make ten.
Five of the seven objects still need to be added.
- 3
Add the remaining five.
All objects from both parts are now included in the whole fifteen.
15; 8 + 7 = 15.
Try it yourself.
Check your understanding
A whole is twelve. Its parts are ten and a blank. What is the blank?
Show answer & reasoning
2
The whole is twelve and one part is ten. Two more complete it because .
Keep practising
6 worksheet questions
Read the questions online
- The parts are four and six. What is the whole?
- The whole is eleven. One part is eight. Find the other part.
- The whole is eighteen. One part is ten. Find the other part.
- Draw a part–whole model for parts seven and five.
- A model has whole sixteen and parts nine and six. Is it correct? Explain.
- Choose two different parts for a whole of thirteen.
Read the worked solutions
- The parts are four and six. What is the whole?
.
10 - The whole is eleven. One part is eight. Find the other part.
.
3 - The whole is eighteen. One part is ten. Find the other part.
Ten and eight make eighteen.
8 - Draw a part–whole model for parts seven and five.
; label the whole and both parts.
A whole of 12 with parts 7 and 5. - A model has whole sixteen and parts nine and six. Is it correct? Explain.
The parts must add to the whole.
No. Nine and six make fifteen, not sixteen. - Choose two different parts for a whole of thirteen.
. Accept any two whole-number parts totalling thirteen.
For example, six and seven.
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Year 1 additive situations and number bonds within twenty.
Official curriculum source ↗